Para-axon initial segment (AIS) and juxtapara (JXP)-AIS are found in other neuronal types. Triple immunostaining of ankyrin G (AnkG) (A, F, K), contactin-associated protein (Caspr) (B, G, L) and voltage-gated potassium channel (Kv)1.1 (C, H, M) (merged in D, E, I, J, N, O) along the axon of P21 cortical neurons (A-E and F-J) and of adult Purkinje cells (K-O). Red brackets (C, H) indicate the Kv1.1+ AIS and JXP-AIS separated by the Caspr+ para-AIS, shown by the green bracket (B, G). In Purkinje cells, only one red bracket shows the Kv1.1+ JXP-AIS, contiguous to the Caspr+ para-AIS (L); the anti-Kv1.1 antibody also labels pinceau synapses around the AIS.